1. Field of the Invention
The present invention relates to an olefin polymerization catalyst component, an olefin polymerization catalyst and a process for producing an olefin polymer. In more particular, the present invention relates to a process for producing an olefin polymer, particularly a linear low density polyethylene by using a transition metal complex having a cyclic structure where two oxygen atoms are bonded with the transition metal atom and further containing a hetero atom in a substituent not contained in the cyclic structure as a main catalyst component for the polymerization of olefins.
2. Prior Art
Many reports have been already published about methods for producing an olefin polymer with a metallocene complex. For example, in Japanese Unexamined Patent Publication Sho No.58-19309, a process for producing an olefin polymer with a metallocene complex and an aluminoxane is reported. However, there was a problem in that the molecular weight of the olefin polymer obtained was low when an olefin was polymerized with the system using bis(cyclopentadienyl) zirconium dichloride and methylaluminoxane.
To address this problem, in WO Publication No. 87/02370, the usage of a reaction product of an organic compound having at least two hydroxy groups with a transition metal compound is reported. But, in the system using 2,2'-thiobis(6-tert-butyl-4-methylphenoxy)titanium dichloride and methylaluminoxane in the report, there was a problem in that although its molecular weight was properly high at an advantageous reaction temperature in an industrial process, the activity was low.
In Japanese Unexamined Patent Publication Hei No. 5-230133, a process for polymerizing propylene or ethylene by using 2,2'-thiobis(6-tert-butyl-4-methylphenoxy)titanium dichloride, triisobutylaluminum and triphenylmethyltetrakis(pentafluorophenyl)borate is disclosed, but the polymerization temperature is too low from the viewpoint of an industrial process.
On the other hand, in Japanese Unexamined Patent Publication Hei No.6-192330, there is disclosed a process for copolymerizing ethylene with an .alpha.-olefin at 80.degree. C. with 2,2'-thiobis(6-tert-butyl-4-methylphenoxy)titanium dichloride, triisobutylaluminum and dimethylaniliniumtetrakis(pentafluorophenyl)borate, but there was a problem in that a large amount of triisobutylaluminum was used.